Means and method of depositing thin films on substrates



June 15, 1965 JAMES E. WEBB 3 ADMINISTRATOR OF THE NATIONAL AERONAUTICS AND SPACE ADMINISTRATION MEANS AND METHOD OF DEPOSITING THIN FILMS ON SUBSTRATES Filed April 18. 1962 INVENTOR. Em; gufiaerfepsmalqcy 2%ORNEY? United States Patent 3,189,535 MEANS AND METHOD OF DEPOSITING THIN FILMS 0N SUBSTRATES James E. Webb, Administrator of the National Aeronautics-and Space Administration, with respect to an invention of Hubert Erpenbach Filed Apr. 18, 1962, Ser. No. 188,594

6 Claims. (Cl. 204-298) This invention relates to means and method of depositing thinfilms on substrates, and included in the objects of this invention are:

First, to provide a means and method of depositing thin films on substrates which is particularly adapted to effect uniform deposition of thin metallic films of refractory metal on ceramic spheres at high temperatures.

Second, to provide a means and method of this class wherein the film itself may be applied by one of several techniques such as sublimation, electronic bombardment, thermal evaporation, or sputtering.

Third, to provide a means and method of this class wherein the ceramic sphere to be coated is vibrated and caused to rotate in a random manner so as to effect an even coating.

Fourth, to provide a means and method of coating ceramic spheres which are adapted to effect coating of the sphere with niobium.

With the above and other objects in view, pear hereinafter, reference is directed to the ing drawings in which:

FIGURE 1 is a diagrammatical view illustrating a bell jar, and showing one means of depositing thinfilms on substrates;

as may apaccompany- FIGURE 2 is an enlarged, partial sectional view, partial elevational view, taken through 2-2 of FIGURE 1; FIGURE 3 is an enlarged, detailed sectional viewtaken within circle 3 of FIGURE 2, showing the workpiece, its support, and the surrounding means for effecting deposition of a metallic film on the workpiece;

FIGURE 4 is a view similar to FIGURE 3 indicating diagrammatically the zone of the workpiece which would be coated were it not for the vibration of theworkpiece;

FIGURE 5 is a fragmentary, diagrammatical view similar to FIGURES 1 and 4, showing a modified means for effecting coating of the workpiece in which the coating is effected by electron bombardment;

FIGURE 6 is a similar fragmentary, diagrammatical view illustrating the arrangement to effect thermal evaporation of a metal to be deposited; and

FIGURE 7' is a similar diagrammatical view illustrating the arrangement utilized for sputtering the coated metal.

Reference is first directed to FIGURES 1, 2, 3 and 4. The apparatus here illustrated is in the nature of laboratory apparatus to simplify the illustration. The apparatus includes a base 1 on which is sealably fitted a bell jar 2, a mounting post 3 extends into the bell jar and carries a laterally extending bracket 4 which supports a solenoid coil 5.

The solenoid coil 5 receives an armature 6, the ends of which are attached to nonmagnetic shaft sections 7 and 8. The proportions of the solenoid coil and armature are such that when alternating current is applied to the solenoid coil, the armature 6 is caused to vibrate vertically. The mounting post 3 may also carry the conductors for supplying current to the solenoid coil 4.

A cooling coil 9 surrounds the shaft section 8 above the solenoid coil 5, this cooling coil is in the form of a tube. The ends of which extend outside the bell jar so that a coolant may circulate therethrough from a source not shown.

The shaft section 8 is provided with a collar 10 above the cooling coil 9 which supports a lower heat shield 11.

The upper end of the shaft section-8 is reduced in diameter and externally screw threaded to receive an adapter, sleeve 12. An upper heat shield 13 isloosely retained between the upper end of the shaft 8 and the adapter 12.

Secured within the upper end of the adapter sleeve 12 is a ceramic extension 14 which projects vertically thereabove. Its upper extremitive is provided with acavity 15 which preferably defines a spherical segment. The upper end of the ceramic extension 14 is adapted to support in stable equilibrium a spherical workpiece W.

A'sccond mounting post 16 extends upwardly in the Operation of the apparatus shown in FIGURES 1 through 4 is as follows:

A spherical workpiece preferably formed of a nonconducting ceramic material is placed on the upper end of the ceramic extension 14. It is preferred that the workpiece have a smooth void free surface.

The material from which the workpiece is formed depends upon the use of which it is to be put. For example, it is desirable in the field of cryogenics to use a synthetic sapphire and coat the sapphire with a metal, such as niobium, usable under cryogenic conditions. The band 18 in this case is formed of niobium.

After the workpiece W and the band 18 have been properly positioned, the bell jar is set in place and a high vacuum is established within the bell jar. Current is then applied to the metal band 'sufiiciently to raise its temperature to a point near melting point of the metal so that there is produced within the cylindrical space defined by the band, an atmosphere rich in the vapor of the metal from which the band is formed.

If the workpiece remained stationary within the metal vapor zone established by the band, a corresponding zone coating W1 of the workpiece would occur as shown in FIGURE 4. However, the solenoid; coil is energized to cause vertical vibration of the armature and the ceramic fact that the workpiece is caused to vibrate and move randomly around its center, other means may be utilized to effect a coating. Thus as illustrated in FIGURE 5, the coating may be perfected by electronic bombardment. More specifically an anode 19 formed of the material to be evaporated on the workpiece is positioned above the workpiece. Between the anode 19 and the workpiece there is provided a focusing coil 20 surrounded by a shield 21. If the workpiece W did not vibrate the upper; surface W3 only would be coated as indicated in FIGURE 5. However, by reason of the random vibration of the workpiece about its center, all portions are uniformly coated.

Reference is now directed to FIGURE 6. Instead of resistance heating of the material to be deposited on 

1. MEANS FOR DEPOSITING THIN METALLIC FILMS ON SPHERES, COMPRISING: (A) A VERTICALLY DISPOSED SUPPORTING ROD RECESSED AT IT UPPER END TO SUPPORT A SPHERICAL WORKPIECE WITH THE MAJOR SURFACE OF THE WORKPIECE EXPOSED ABOVE THE SUPPORTING ROD; (B) MEANS FOR VIBRATING SAID ROD THEREBY TO VIBRATE SAID WORKPIECE TO CAUSE RANDOM ROTATION THEREOF ON SAID SUPPORTING ROD; (C) AND MEANS FOR TRANSFORMING A METAL INTO A STATE CAPABLE OF DEPOSITION AND CAUSING SAID METAL TO DEPOSIT ON THE SURFACE OF SAID RANDOMLY ROTATING WORKPIECE. 